what makes a sub caliber a sub caliber?

[pTa]

I thought sub meant UNDER 1". So all small arms weapons would be sub caliber. Now I get the military police aspect.
So, sub law enforcement or military use is sub caliber?

[Fjold]

So, its not a caliber for using on submarines???

Nope, on Submarines we used 1911s in 45 ACP, M14s in 308 and 12 Gs in Ithaca 37s.

Subcaliber in handguns is anything less than .40 and in rifles anything under .375.

[Swift Justice]

Sub-caliber just means a round smaller than that which the firearm is normally intended to fire. A .22.lr conversion unit for an AR-15 is a sub-caliber conversion. A 22 lr conversion unit on a 1911 is sub-caliber.

This is correct. Any weapon that can fire a projectile smaller than what the barrel is actually designed to fire by way of some type of adapter or insert is referred to as "sub caliber". You see this often referred to in military literature as "sub caliber munitions", which often refers to training adapters and rounds for tanks that allow them to shoot smaller/cheaper ammunition than what is normally shot.

A .45 with some type of .22 adapter would be sub-caliber, so would a Glock. One would think that an AR with a .22 bolt conversion would also be considered sub caliber, but the round is actually the same diameter as what the barrel was originally designed for...

[Heiko]

Sub caliber versus major caliber for IDPA type competition classes? Just a guess....

[Ranger20]

I always thought this was a SUB CALIBER... Sorry Couldn't resist





Here is a SUB Caliber... A sabot used to fire a smaller caliber round than the bore of the gun. I have 30:06 rounds that use a Sabot to fire a 223 round. This picture is an example.